You are inside your opponents guard.
Grab both of your opponents biceps and keep your elbows down.
Come up on your left foot and twist your body to the side, this creates space between you and your opponents right leg. Be sure that your left foot is not too far forward, otherwise your opponent may grab it.
Slide your left hand between your stomach and your opponents right leg. Place this hand on the ground so your opponents right leg is on your left shoulder.
Reach over your opponent with your left hand and grab the left side of their collar with your thumb on the inside. Try to get a deep grip with this hand, ideally your fist should be touching the ground. Be sure to always keep your head up to prevent your opponent attempting the Triangle Choke.
Put your left knee back down the on the ground and come up on your right foot. Walk round to the side of your opponent, pushing your left elbow down to the ground to the right of your opponents head. Now lean over your opponent to force their knees to the ground. This should cause them to uncross their feet.
When your opponent uncrosses their feet, bring your head under their right leg.
To finish simply bring your right hand from under your opponents right leg and take up the side mount.